How to use php serialize() and unserialize()

Question

My problem is very basic.

I did not find any example to meet my needs as to what exactly serialize() and unserialize() mean in php? They just give an example - serialize an array and show an output in an unexplained format. It is really hard to understand the basic concept going through their jargon.

EDIT:

<?php

$a= array( '1' => 'elem 1', '2'=> 'elem 2', '3'=>' elem 3');
print_r($a);
echo ("<br></br>");
$b=serialize($a);
print_r($b);

?>

output:

Array ( [1] => elem 1 [2] => elem 2 [3] => elem 3 ) 

a:3:{i:1;s:6:"elem 1";i:2;s:6:"elem 2";i:3;s:7:" elem 3";}

I cannot understand the second output. Besides that, can anyone give an example of a situation that I need to serialize a php array before using it?

Answer 1

<?php
$a= array("1","2","3");
print_r($a);
$b=serialize($a);
echo $b;
$c=unserialize($b);
print_r($c);

Run this program its echo the output

a:3:{i:0;s:1:"1";i:1;s:1:"2";i:2;s:1:"3";}

---

here
a=size of array
i=count of array number
s=size of array values

you can use serialize to store array of data in database
and can retrieve and UN-serialize data to use.

Answer 2

Most storage mediums can store string types. They can not directly store a PHP data structure such as an array or object, and they shouldn't, as that would couple the data storage medium with PHP.

Instead, serialize() allows you to store one of these structs as a string. It can be de-serialised from its string representation with unserialize().

If you are familiar with json_encode() and json_decode() (and JSON in general), the concept is similar.

Answer 3

From http://php.net/manual/en/function.serialize.php :

Generates a storable representation of a value. This is useful for storing or passing PHP values around without losing their type and structure.

Essentially, it takes a php array or object and converts it to a string (which you can then transmit or store as you see fit).

Unserialize is used to convert the string back to an object.

Answer 4

PHP serialize() unserialize() usage

http://freeonlinetools24.com/serialize

echo '<pre>';
// say you have an array something like this 
$multidimentional_array= array(
    array(
        array("rose", 1.25, 15),
        array("daisy", 0.75, 25),
        array("orchid", 4, 7) 
       ),
    array(
        array("rose", 1.25, 15),
        array("daisy", 0.75, 25),
        array("orchid", 5, 7) 
       ),
    array(
        array("rose", 1.25, 15),
        array("daisy", 0.75, 25),
        array("orchid", 8, 7) 
    )
);

// serialize 
$serialized_array=serialize($multidimentional_array);
print_r($serialized_array);

Which gives you an output something like this

a:3:{i:0;a:3:{i:0;a:3:{i:0;s:4:"rose";i:1;d:1.25;i:2;i:15;}i:1;a:3:{i:0;s:5:"daisy";i:1;d:0.75;i:2;i:25;}i:2;a:3:{i:0;s:6:"orchid";i:1;i:4;i:2;i:7;}}i:1;a:3:{i:0;a:3:{i:0;s:4:"rose";i:1;d:1.25;i:2;i:15;}i:1;a:3:{i:0;s:5:"daisy";i:1;d:0.75;i:2;i:25;}i:2;a:3:{i:0;s:6:"orchid";i:1;i:5;i:2;i:7;}}i:2;a:3:{i:0;a:3:{i:0;s:4:"rose";i:1;d:1.25;i:2;i:15;}i:1;a:3:{i:0;s:5:"daisy";i:1;d:0.75;i:2;i:25;}i:2;a:3:{i:0;s:6:"orchid";i:1;i:8;i:2;i:7;}}}

again if you want to get the original array back just use PHP unserialize() function

$original_array=unserialize($serialized_array);
var_export($original_array);

I hope this will help

Answer 5

When you want to make your php value storable, you have to turn it to be a string value, that is what serialize() does. And unserialize() does the reverse thing.

Answer 6

Please! please! please! DO NOT serialize data and place it into your database. Serialize can be used that way, but that's missing the point of a relational database and the datatypes inherent in your database engine. Doing this makes data in your database non-portable, difficult to read, and can complicate queries. If you want your application to be portable to other languages, like let's say you find that you want to use Java for some portion of your app that it makes sense to use Java in, serialization will become a pain in the buttocks. You should always be able to query and modify data in the database without using a third party intermediary tool to manipulate data to be inserted.

it makes really difficult to maintain code, code with portability issues, and data that is it more difficult to migrate to other RDMS systems, new schema, etc. It also has the added disadvantage of making it messy to search your database based on one of the fields that you've serialized.

That's not to say serialize() is useless. It's not... A good place to use it may be a cache file that contains the result of a data intensive operation, for instance. There are tons of others... Just don't abuse serialize because the next guy who comes along will have a maintenance or migration nightmare.

A good example of searilize() and unsearilize() could be like this:

$posts = base64_encode(serialize($_POST));
header("Location: $_SERVER[REQUEST_URI]?x=$posts");

Unsearilize on the page

if($_GET['x']) {
   // unpack searilized and ecoded URL
   $_POST = unserialize(base64_decode($_GET['x']));
}